Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $33.27   5.167%   $34.9891   $34.99   $35.00   $35.00  
  Purchase #2 $42.45   3.265%   $43.836   $43.84   $43.85   $43.80  
  Purchase #3 $187.43   10.775%   $207.6256   $207.63   $207.65   $207.60  
  Purchase #4 $238.29   3.181%   $245.87   $245.87   $245.85   $245.90  
  Purchase #5 $54.98   8.220%   $59.4994   $59.50   $59.50   $59.50  
  Purchase #6 $213.90   8.425%   $231.9211   $231.92   $231.90   $231.90  
  Purchase #7 $236.39   4.113%   $246.1127   $246.11   $246.10   $246.10  
  7 purchase totals = $1,006.71       $1,069.8539   $1,069.86   $1,069.85   $1,069.80